sclass Splitter1<A> {
  new MultiSet<A> aExamples;
  new MultiSet<A> bExamples;
  
  // 1 for A, 2 for B, 0 for unknown
  int get(A a) {
    int i = aExamples.get(a)-bExamples.get(a);
    ret i > 0 ? 1 : i < 0 ? 2 : 0;
  }
  
  void learn(A a, bool isB) {
    (isB ? bExamples : aExamples).add(a);
  }
  
  void clear { aExamples.clear(); bExamples.clear(); }
}